Process and device for the production of electrolytic condensers



June 20, 1939.

B. SPRINGER 2,163,213

PROCESS AND DEVICE FOR THE PRODUCTION OF ELECTROLYTIC CONDENSERS FiledApril 13, 1937 li theaidoia PM June so, 1939 r'aocsss AND DEVICE FOR THEPBODUC- H0801 ELEUIIOLTTIO' OOND Springer. Berlin-Schoncberg, Germanyapplicationapril 13, In Germany sauna. (Cl. 115-315) For the productionor the highest grade electrolytic condensers it is very important thatthe intermediate layer between the two plates which contains theelectrolyte should be as thin as 5 possible so that the current path inthe electrolyte is a minimum and so that thereby the resistance isreduced to as small a value as possible. It would be most satisfactoryif as thin as possible a sheet of the electrolyte could be used withoutany other support.. This however is impossible on account of theproperties of the electrolyte and it is necessary to provide a supportfor the electrolyte in the form of an absorbent porous body. At presentmultiple layers of paper are used as a support in: the electrolytef 1rpaper is to be used it must be made without, or substantially withoutsize. It must also be kept as thin as possible for the reason set outabove. Unsized paper of small strength has a correspondingly smallrigidity which is practically completely lost when it becomesimpregnated. This increases the difflculty of working with it to amaximum so that it .has not been possible hitherto to eiIec't thenecessary impregnating of the paper with the electrolyte in a completelysatisfactory manner.

It is the subject of the invention to make this possible and this isrealised in that a solution of the electrolyte is prepared by heating inthe so as to produce a super-cooled, super-saturated solution with whichthe evacuated roll comprising the electrodes and the absorbent'porousintermediate layer (paper) is impregnated in vacuo the vacuum being thenremoved and the complete impregnation of the electrolyte effected byheating the roll in the electrolyte.

As electrolyte a known mixture of boric acid, glycol or glycerine andammonia is used. This mixture is brought to the necessary concentra- QOtion by heating in the known way. Its boiling point lies'approximatelyat 115 C. The correct concentration is, however, in some cases onlyreached ata boiling pointof 132-C. In such .cases it is heated furtheruntil this boiling point is reached.

According to the invention it has further been established that theheating only needs to be carried out to a boiling point of 125 C. forproducing the super-cooled solution and the flnal 50 heatingtoaboilingpoint of 132 C.cantake place later after removing the vacuumwhen the roll impermeated with the electrolyte is heated.

The carrying out ottheprocess according to the invention canconveniently take place with receptacle for holding the roll into normalway, this solution is then rapidly cooled 1937, Serial No. 1363:

April 15, 1936 which the electrolyte fluid can be passed from a supplycontainer without air having access at the,

- same time. This can be. arranged in a simple manner in that the supplycontainer ior'the electrolyte fluid is connected to the evacuable recep-5 tacle by way.of a valve which is arranged at a point in the supplycontainer which remains always below the level of the fluid. For examplethe supply container can with advantage be ar-' ranged on the cover ofthe receptacle and can 10 giect with the latter by way of a valve in itsIn the attached drawing there is shown an embodiment of the device forcarryingout the process according to the invention.'

The device comprises a base plate I for example of iron which possessesone or more apertures 2. To these apertures is connected a vacuum pump3' by means of a conduit 5 adapted to be closed by a valve 4. On thebase plate! is set a receptacle comprising a cylinder S, for example ofglass, and a cover plate I, ifor example of aluminium or other lightmaterial. The pack- .ing between the cylinder and the base plate I orbetween the cylinder and the cover plate I .comprises rings i and 9 ofrubber or the like. The

cover plate I possesses a flat under-surface in order to be easilyremovable andlies' solely on the corresponding flat rubber' ring 9 onwhich it is adapted to be pressed by reason of the reduced pressure inthe receptacle. In the cover plate I is inserted a manometer l0. Inaddition the cover plate possesses an aperture l2 closable by means of aplug H and preferably conical in shape. On the upper side of the coverof the receptacle which is also flat is disposed a supply container 14for 'the electrolyte fluid this also being supported on an intermediaterubber disc l3. 'Ihis possesses a basalaperture I! which is preferablyconical and which may be produced 40 to form .a small channel whichprojects into a corresponding hole It in the cover plate I and isadapted to be closed by means of a valve member I! provided with handleportion IT. The condensers It to be impregnated are placed inside thelower receptacle'preferably in a separate receptacle II. The size of thereceptacle 2! is adapted to the number of condensers to betreatedsimultaneously. The-size of the supply container H is adjusted sothat it can hold an amount of fluid Went for completely covering thecondensers in the receptacle 2'.

The carrying out of the process according to the invention with the aidof the devicedescribed takes place as follows: j

First, the known electrolyte solution '01 glycol, 'boric acid and'ammonia is prepared and heated until is possesses a boiling point ofabout 125 C. preferably:

Grams .Boric acid 620 Ethylene glycol 580. 25% ammonia 140" are mixedtogether. This solution is cooled as rapidly as possible, for example bysetting it in' ,cold water, and it has been established that ifconsiderable mechanical disturbance is avoided no separation of crystalstakes place but a supercooled, super-saturated solution is produced, theboiling point of which ina vacuum corresponding to a pressure of mm. ofmercury i'sat room temperature. At the same time or before or after; therolls are heated for about two hours I aleazis densers havingabsorbent,porous, intermediate layers consisting in evacuating the condenserbodies, adding a supercooled solution of an electrolyte of the'polyhydroxy alcohol, weak acid salt type, which has been heateduntil'the solutionhasa certain boiling point to the evacuated condenserbodies so as to cover them, destroying the vacuum to which thecondenser. bodies are subjected and finally heating the bodies in theelectrolyte solution. r

2. A process for impregnating electrolytic condensers having absorbent,porous, intermediate 'layers consisting in evacuating the condenserbodies, adding a supercooled solution of an electrolyte of thepolyhydroxy alcohol, weal; acid salt type, which has been heated untilthe solu- .at approximately 100? C. in order to dry them 7 0 completely.This heating can take place either within or outside the impregnatingdevice. The

rolls are then placed in the device and evacuated for about an hour at'a pressure of 10 mm.' of mer-' cury. It'is possible alternatively to dowith a less I intense drying but normally this necessitates a longerperiod for evacuation.

Thesuper-cooled electrolyte fluid isthen carefully poured into the-upperreceptacle l4 andthe valve 4%; carefully opened. Theelectrolytefluid-accordingly flows into the receptacle 20' without air being ableto enter. The vacuum is accordingly maintained.- The pressure may beprevented from rising above about 15 mm; of

mercury by operatingthe pump.

As soon as the rolls are completely covered, at

which time the electrolyte has to be caused to' iimpermeate the pores"of the evacuated and very porous material, the .cock is opened and thetrolyte well into thepores. In'order torealize the complete impermeationof the porous inter mediate layer the receptacle!!! then-heated superiorto all the known condensers since" the tric'streng'th. g

' The carrying out of the process according to receptacles, theirrelative position, the establish-.

' 1, A process for impregnating electrolytic conimmediatelya Theelectrolyte.then becomes of low viscosity and can thus fill all thepores of the absorbent porous intermediate layer. The

heating is continued: until the electrolyte reaches the boiling point of132C. It has been established that in this way condensers can beproduced which are considerably 'thin' layers holding theelectrolyte'which arenow able to be used give the finished condenserparticularly small dimensons, and -moreover the complete impregnationproduces a-high dielecthe invention is of course not limited to the.device shown but tbis'maybe .varied in' the most diverse ways asregards the construction of the mentof a connection'between the two.receptacles without destroying the vacuum, etc., without departingfrom'the scope of {the invention.

I claim:

vacuum is destroyed by withdrawal of the plug H. The. external pressurenow presses 'the-e1ec-- tionhas a'boiling point of 0., to the evacu-'ated condenser bodies so as to cover them, de-:

stroying the'vacuum to "which the condenser bodies are subjectedandfinally heating the bodiesin the electrolyte solution. until aboiling;

point of 132 C. is 'reached.

3. A process for impregnating electrolytic con- "densers havingabsorbent, porous, intermediate layers consisting in drying thecondenser bodies by heating, evacuating said dry condenser bodies,

covering said evacuated bodies with an electro- .lyte solutioncontainingboric acid, glycol and ammoniawhi'ch hasbeen heated until thesolution has a boiling point of about 125 0., and

. rapidly cooledto room temperature to produce a supercooled, Saturatedsolution, while main- .taining the vacuum,- destroyingthe vacuum and.finally heating the solutionand bodies until a boiling point of about132 C. is reached.

. 4. A process for impregnating electrolytic con;- densers havingabsorbent-porous, intermediate layers consisting in drying:condenserbodies by',

heating, evacuatingsa'id dry condenser bodies, covering said evacuatedbodies with an electrolyte solution containing ,boric acid,- glycerineand boiling point of about 132 'CQis reached.

'- -5. A' process for impregnating electrolytic condensers havingabsorbent; porous, intermediate finally heating the'solution' and bodiesuntil 'a boiling pointoi ab'out132 c. is, reached. Y

layers consisting in drying condenser "bodiesby heating. toapproximately 15!)" 0., evacuating said dry condenser bodies'at'apressure of about 10. millimeters of mercury. covering saidevacuatedbodies with an electrolyte solution, containing' 620 grams ofboric acid, 580 grams ethyl-,

ene glycol and grams of ammonia, which has been heated the solution hasa point I of about 125 C.,and rapidly cooled to .room temperature toproduce a'supercooled, Saturated solution'whichboilsat room temperaturewhen subjected to a vacuum corresponding to a pressure of 15 millimetersof mercury, while mainthe vacuum, destroying the vacuum and

